Imagine: No more fumbling for credit cards or digging through your pockets for loose change. The technology already exists to let you buy a grande soy latte through your phone, simply by saying your name out loud at the register.

As the number of neighborhood bank branches dwindles, Americans increasingly use their mobile phones to manage money and shop. Payments made via mobile devices in the United States are expected to total $90 billion by 2017, a big jump from the $12.8 billion spent in 2012, according to Forrester, a research and advisory firm in Cambridge, Mass.

Privacy advocates worry that the emergence of “mobile wallet” technology will leave consumers more vulnerable than ever to identity theft and invasive data collection.

“All of a sudden the mobile phone is about to be transformed beyond a spy in your pocket to your bank, your mortgage lender and your landlord,” said Jeffrey Chester, the executive director of the nonprofit Center for Digital Democracy in Washington. “In a way, it’s kind of a privacy tipping point, because one single device knows wherever you go, your geographic history, your social media connections and your financial behaviors.”

One of the most popular mobile payment systems, Square, enables sellers to accept credit cards through a small device attached to a cellphone or tablet.

Consumers who install the “Square Wallet” app on their phones can pay for an item at participating businesses like Starbucks without ever having to pull out their wallets — or even their phones. Instead, they can just say their names to pay. A photo and the name of the customer pops up at the register, and the cashier taps the picture to authorize the sale, automatically charging the customer’s account.

Walla.by, a cloud-based wallet app, allows consumers who input their credit card information to see which card will get them the most rewards or cash back for each purchase. The app also helps consumers take advantage of special offers from banks and merchants.

PayPal, Google and other companies offer similar digital wallets.

Such technologies offer convenience and real-time deals to consumers while allowing companies to better track customer behavior and test marketing strategies. But the Federal Trade Commission warned in a report this month that these mobile technologies come with hidden costs and risks.

Advertisers, retailers, operating system manufactures and app developers can use the data collected from mobile devices to build more comprehensive consumer profiles, including shoppers’ personal contact information, details of their purchases and their physical locations, the report said.

For now, consumer protections for mobile payments aren’t really on policymakers’ agendas, said Chris Jay Hoofnagle, director of information privacy programs at the Berkeley Center for Law & Technology at the University of California, Berkeley. “The FTC knows about these problems and it has written about them, but we’re very early in this process and these types of data transfers are not noticeable to the consumer, so one question is will the consumer ever object?” he said.

“Going to mobile payments — unless rules are put in place — will be zero privacy,” he said.

Hoofnagle suggests modernizing a California law that prohibits brick-and-mortar businesses from asking for personal contact information such as a ZIP code and phone number from consumers who pay by credit card. The idea, he said, would be to extend those protections to the digital space.

As the popularity of mobile payments grows, companies’ privacy practices could face more scrutiny.

Google Wallet recently came under fire when an Australian app developer complained in a blog that Google was sending him the names, physical addresses and e-mails of customers who bought his app on Google Play, the company’s store for Android apps, games, music, books, movies and other digital content.

In response to a letter of inquiry from Democratic Rep. Hank Johnson of Georgia, Google said that it discloses in its Google Wallet privacy notice “that we may share your personal information with third parties as necessary to process your transaction and maintain your account.”

Information such as name and e-mail address “is necessary for developers to issue refunds, reversals, payment adjustments ... and investigate chargebacks,” Google said in its written response to Johnson.

With less than hour to spare, the Senate late Friday backed legislation averting a government shutdown as coal-state Democrats retreated on long-term health care benefits for retired miners but promised a renewed fight for the working class next year.